Such an expansion likely would generate more sales, but it's unknown whether the service would make money or break even.

Amazon.com launched its same-day service in New York earlier this year. If orders are received by 11 a.m., products can be delivered to select areas by the end of the day, Bhaskaran said. In some areas around Manhattan, he said, products are delivered the next morning. Cost varies based on the product that's shipped and its weight.

Edward Weller, an analyst with ThinkEquity Partners in San Francisco, said the same-day shipping program is a tiny part of Amazon.com's operations and the company has disclosed very little about it.

Bezos has credited Amazon Prime, which started in February 2005, for boosting sales because, he said, customers shop in more retail categories.

Bezos has said in the past that the delivery service hasn't made money.

Last month, Amazon.com said that first-quarter profits more than doubled from a year ago to $111 million, or 26 cents per share, thanks to healthy electronics and apparel sales. Analysts had forecast a profit of 15 cents per share.

Amazon.com also predicted rosy sales growth of up to 31 percent to $14 billion for the year, even though many brick-and-mortar retailers have predicted an upcoming sales slowdown because of rising gas prices and a sagging housing market.

Bhaskaran's comments came a day after Amazon.com said it has taken more than 1 million pre-orders for "Harry Potter and the Deathly Hallows," the seventh and final book of the series about a boy wizard and his fight against evil.

The company said last month that customers in all states except Alaska or Hawaii who select standard shipping or better, including Amazon Prime, would be guaranteed delivery of the book on its release date of July 21 or the cost of the book would be refunded.

Bhaskaran, formerly director of logistics for The Gap, said Amazon.com has not set a cut-off date for when the order must be placed.

Amazon.com has reduced the price of the hardcover edition to $17.99 from $18.89, and customers who already pre-ordered the book will be charged the lower price, the company said.